from tkinter import *
from tkinter import filedialog
root = Tk()
root.geometry('400x300')
root.title('Текстовый редактор')
root.resizable(False, False)
def file_open():
	url = filedialog.askopenfilename()
	f = open(url)
	text.delete(0.0, END)
	text.insert(0.0, f.read())
	f.close()
def file_save():
	url = filedialog.asksaveasfilename()
	f = open(url, 'w')
	f.write(text.get(0.0, END))
	f.close()
rootmenu = Menu(root)
root.config(menu = rootmenu)
fm = Menu(rootmenu, tearoff = 0)
fm.add_command(label = 'Открыть', command = file_open)
fm.add_command(label = 'Сохранить', command = file_save)
rootmenu.add_cascade(label = 'Файл', menu = fm)
text = Text(width = 300, height = 400)
text.pack()
root.mainloop()